This invention relates to a magnetic recording and reproducing device, and more particularly to a magnetic recording and reproducing device for recording video signals intermittently on a magnetic tape by rotary heads and reproducing the signals, for example, as a quick motion image or a still image.
Usually, in a magnetic recording and reproducing device for recording a video signal, which is taken out at every n fields (n being an integer), intermittently on a magnetic tape moving at a speed of 1/n of the standard speed, there is sometimes caused distortion (so-called skew) in the reproduced image because the scanning trace of the magnetic head on the magnetic tape becomes different at different tape moving speeds.
For example, referring to FIG. 1, the video signal is recorded as tracks 1a and 1b on a magnetic tape a reduced tape moving speed, and when the video signal is reproduced at the usual tape speed (according to the Standard of E I A J, this speed is 19.05 cm/sec. E I A J is the Electric Industrial Association of Japan), the scanning trace of the magnetic head 3 is as shown at 2. That is, two adjacent tracks are reproduced at the same time during one scanning of the head 3. In this case, if there is no continuity between horizontal synchronizing signals reproduced from the track 1a and successively from the track 1b, the reproduced image is skewed. Therefore, for a standard type video tape recorder according to the standards of E I J A, the number of the horizontal synchronizing signals to be recorded in a length 1 between an intersection A of the track 1b and a line from the start point of the track 1a perpendicular to the adjacent track 1b and the start point of the track 1b, as shown in FIG. 1, is set to be 4.5 H so as to make the horizontal synchronizing signal continuous between the adjacent tracks, and further the vertical synchronizing signal is arranged so as to be at a constant position on the magnetic tape.
However, in such a recording pattern, although there is no problem when signals for an odd field and an even field are alternately recorded so that there are odd and even field signals on adjacent tracks, when recording only the odd field signals or even field signals successively the phase of the horizontal synchronizing signal becomes different. Thus, skewing of the image reproduced at the standard tape speed can be prevented by recording alternately the even field signals and the odd field signals when recording the video signal intermittently. However, such a recording method requires a complex circuit configuration for a video tape recorder employing a plurality of tape moving speeds. That is, the dividing ratio of dividing circuits connected to a gate, which is used for recording the video signal intermittently and which divides the vertical synchronizing signal of the video signal or the rotation phase signal of a rotary head, should all be odd. Therefore, it is necessary to provide parallel dividing circuits connected to the gate corresponding to the number of the tape moving speeds. On the other hand, when only the odd or even field signals are recorded intermittently, the dividing ratio may be even, and so the dividing circuits can be connected in series even for a plurality of the tape moving speeds and the circuit configuration becomes very simple. FIG. 1 is for the case when the intermittently recorded video signal is reproduced at the standard magnetic speed as a quick motion picture, but even when the video signal is reproduced as a still image by stopping the magnetic tape and scanning a single track, there is also caused skewing in the reproduced still image owing to discontinuity of the horizontal synchronizing signal, as described hereinafter.